A silicon wafer having various semiconductor devices patterned on a surface thereof is divided into semiconductor chips of a prescribed size along border lines between adjacent patterns. As a method for dividing a silicon wafer into semiconductor chips, dicing, scribing, and other methods are known.
According to scribing, scribe lines are formed on a surface of a silicon wafer along borders between adjacent semiconductor patterns that are to be semiconductor chips, in consideration of the crystalline orientation of the silicon wafer. After scribing, the silicon wafer is divided into a plurality of semiconductor chips. The scribe lines are formed by pressure-contacting a diamond piece or the like to the surface of the silicon wafer. Therefore, scribing has the risk of generating cracking or chipping at many positions of the silicon wafer while the scribe line is formed on the surface thereof, depending on the scribe conditions.
In order to avoid this, dicing is usually widely used for dividing a silicon wafer. According to dicing, a blade having grinding diamond granules buried therein is rotated at a high speed so as to cut a silicon wafer along borders between adjacent patterns that are to be semiconductor chips.
However, dicing also involves the risk of generating chipping around the lines along which the silicon wafer has been cut, since the silicon wafer is mechanically cut. When chipping occurs, small broken pieces of the wafer generated by the chipping may undesirably enter the semiconductor chips as foreign objects. The semiconductor chips having such foreign objects may not provide prescribed functions.
For producing a flat display device of, for example, a liquid crystal display apparatus, the following method for forming a scribe line on a glass substrate has been developed in order to divide the glass substrate. According to this method, the glass substrate is continuously irradiated with a laser beam along lines along which the glass substrate is to be divided, while areas of the glass substrate irradiated with the laser beam are continuously cooled. It has been considered to form a scribe line on a silicon wafer using such a method which combines heating with a laser beam and cooling. However, such a method has not been put into practice for the reason that when a surface of a silicon wafer is continuously irradiated with a laser beam while being cooled, the electric functions of the semiconductor devices on the surface of the silicon wafer may be spoiled.
The present invention, for solving such problems, has an object of providing a method for forming a scribe line on a semiconductor wafer, such as a silicon wafer or the like, for dividing the semiconductor wafer without fail and without generating chipping, cracking or the like in the semiconductor wafer; and an apparatus for forming a scribe line usable for the method.